Shields for vacuum tubes and the like



July 6, 1965 G. M. WORDEN, SR

SHIELDS FOR VACUUM TUBES AND THE LIKE 2 Sheets-Sheet 1 Filed Aug. 10,1962 INVENTOR. 687/7654! WOAQlV-Sn y 5 e. M. WORDEN, SR 3,193,610

SHIELDS FOR VACUUM TUBES AND THE LIKE Filed Aug. 10, 1962 2 Sheets-Sheet2 INVENTOR.

G 50/? 66 M Wo/wm/S/a Y zrwa Wm ATTORNEYS United States Patent3,193,61tl SHIELDS FOR VACUUM TUBES AND THE LIKE George M. Worden, Stu,Manhattan, N.Y., assignor, by mesne assignments, to Atiee Corporation,Winchester, Mass, a corporation of Massachusetts Filed Aug. 10, 1962,Ser. No. 219,356 18 Claims. (Cl. 174-35) This application is acontinuation-in-part of application Serial No. 86,650, filed February 2,1961, now abandoned.

This invention relates to vacuum tubes and, more particularly, to aprotective shield therefor.

Ordinarily, high operating temperature has a deteriorating effect uponall types of vacuum tubes, thus shortening their useful life, requiringfrequent maintenance replacement and repairs, and reducing thereliability of the electronic system of which the vacuum tube is acomponent. To avoid such deleterious effects, vacuum tube shields areemployed to remove the excess heat from the tube environment. Inaddition, a tube shield should also act as an electrical shield aroundthe tube to reduce interaction due to stray fields. It should supportthe tube securely in its socket against vibration and impact in anyplane, and it should protect the tube and its leads from mechanicalinjury.

There are three heat transfer paths from a bare tube: radiation from theenvelope to surfaces which the envelope sees, either natural convectionor gaseous conduction from the envelope to the environmental air or gassurrounding the tube, and conduction along the tube lead wires. Inbrief, heavy gage, short length wire leads which are thermally grounded,tend to increase heat transfer by conduction. The terminals of the leads(away from the tube) must be kept cool if conduction is to be at allappreciable. In general, conduction along and convection from long leadwires on subminiature tubes is not appreciable.

The major mode of heat transfer from a bare vacuum tube is radiation.This is because the heat transfer by radiation is a function of thedifference of the fourth power of the absolute temperatures, whereas,convection and gaseous conduction are functions of only the first powerof temperature difference. If a tube is surrounded by lower temperaturesurfaces which are at distances greater than one inch from the tube,natural convection will occur. The heat transferred to these surfaces byconvection will be less than that transferred by radiation. If thesurrounding surfaces are very close, say, less than one-half inch away,and if the tube is enclosed in an airtight container, then freeconvection becomes ineffective and heat will be transfered by gaseousconduction to a smaller degree than that by radiation.

In order to be effective in removing heat from the envelope, the firstand most important consideration is to provide a minimum of contactresistance between the tube shield, its base, and the chassis ormounting surface. The mounting surface should be of metal. Nothing isgained by mounting tube shields on, for example, a phenolic chassis, oron materials of low thermal conductivity. Such materials act as thermalinsulators and it is easily possible to overheat a well shielded vacuumtube, even when it is operated well within its dissipation ratings.Idealy, for maximum heat transfer, the tube shield should be soldered,brazed or bonded to the metal surface to obtain a near perfect contact.Riveting or bolting a shield to a metal surface leaves a thin air gapwhich constitutes an extremely high thermal resistance, probably muchmore than the resistance of the shield itself. For effective heatremoval, this gap must be minimized and preferably eliminated. A poorsurface contact may cause a shielded tube to operate hotter than a baretube, even though other thermal considerations are incorporated in thedesign. It is not advisable to use a tube shield which is not thermallybonded to a cooler metal surface.

In addition, the shield should fit the tube envelope as tightly aspossible to reduce the air gap to a minimum. Perfect contact with thebulb glass is difiicult. One method which has found some use is to applysilicone grease between the tube and the shield. Unfortunately, thismethod is not usually suited to the maintenance techniques of the ArmedServices. In general, the most practical method is to provide someflexibility in the shield to accommodate expansion and variation in bulbdimensions. For example, this can be accomplished by slotting orsplitting the shield.

Further, it is desirable to increase the absorptivity of the innersurface of the shield to increase the heat transfer by radiation fromthe envelope. A brightly polished surface is a poor absorber and shouldnot be used. A dull, oxidized .and blackened surface is preferred. Ifheat transfer by radiation to the surroundings is desired, then the samedull surface should be used on the outer surface of the shield. On theother hand, if temperature sensitive parts and other tubes constitutethe surrounding objects (in which case radiant heat transfer to theseparts is not desired) then the shields outer surface should be highlypolished. Thus, the surrounding objects influence the design of theshield. In general, radiant energy should not be deliberately expendedinside an electronic case. The heat is radiated from the source anddispersed to other parts in an uncontrolled fashion.

Accordingly, an object of the present invention is to provide animproved heat dissipating vacuum tube shield which will effectiveconduct the heat therefrom, thus avoiding overheating and overcoming theaforementioned difficulties.

Another object of the present invention is to provide a heat dissipatingvacuum tube shield which will prevent accidental disconnection of thevacuum tube from its mounting socket.

Still another object is to provide a tube shield which will minimize theeffects of impacts and vibrations to which the tube may be subjected.

It is a further object of this invention to provide a tube shield whichwill not weaken the tube envelope by scratching, scoring or marking theglass.

Still a further object is to provide a vacuum tube shield which can bereadily adapted for use with standardized government specificationparts, as well as commercial parts, to facilitate the use of this shieldon all types of electronics equipment.

The objects of the invention are accomplished by providing an expansibletube shield having a plurality of spring elements secured hereto in anexcellent heat conducting relationship, and adapted to contact thevacuum tube under pressure. The shield is held in a mounting ringsecured to the chassis, so that when fully assembled, the pressure ofthe ring against the shield urges the resilient spring elements againstthe tube to improve the heat transfer and vibration dampeningcharacteristics of the shield. The construction minimizes contactresistance between the shield base and chassis, while the shape of thespring elements enables a reduction of the air gap between themselvesand the tube envelope. The interior surface of the shield may beadditionally finished, as noted above, to further improve the heatabsorption of the shield.

All of the foregoing and still further objects and advantages of thisinvention will be further explained with reference to the followingspecification, taken in connection with the accompanying drawing,wherein:

FIG. 1 is a top perspective view of a vacuum tube Patented July 6, 196523 shield assembly made in accordance with one form of the presentinvention in actual use.

FIG. 2 is an exploded side elevational view, partly in section, of thecomponent parts of the assembly shown in FIG. 1.

FIG. 3 is an enlarged longitudinal cross-sectional view taken along line33 of FIG. 1.

FIG. 4 is a transverse cross-sectional view taken along line 4-4 of FIG.3.

FIG. 5 is an enlarged fragmentary perspective view of certain jointelements of the present invention.

FIG. 6 is an exploded perspective view, partly in section, of a slightlymodified form of construction.

FIG. 7 is a front view, partly in section, of another embodiment of theinvention.

FIG. 8 is an exploded perspective view of the embodiment of FIG. 7.

FIG. 9 is a side view, partly in section, of the hinge structureaccording to this embodiment.

FIG. 10 is a sectional view along the line 19-1t) of FIG. 7.

FIG. 11 is a side sectional view along the line 1111 of FIG. 7.

FIG. 12 is a sectional view along the line 1212 of FIG. 9.

FIG. 13 is a transverse sectional view along the line 13-13 of FIG. 9.

Referring now to the drawing, and more particularly to FIGS. 1 to 5thereof, a vacuum tube shield 16 made in accordance with the presentinvention for use with a standard tube socket 16, is shown to include ashallow cylindrical base 12 having an interior compartment 13 forpurposes hereinafter described, and a radially inwardly directed flange15 at one lower end defining a circular opening 14 receiving the upperend of the tube socket 16 therewithin.

The tube socket mounting ring 18 is secured to the metallic chassis 25by means of bolts 22 and nuts 24, which bolts 22 are also receivedwithin a pair of opposed spaced openings in the flange 15 therebysecuring base 12 upon chassis 25 in proper assembled relationship withtube socket 16. It should be understood that the tube socket mountingring 18 is an integral part of the tube socket 16. The side wall of thebase 12 is also provided with a pair of diametrically spaced apartopenings 26 in the vicinity of the bores 20 to facilitate theinstallation of the parts during assembly.

A vacuum tube having a glass envelope 29 and depending prongs 23, may bemounted in tube socket 16 in a conventional manner within the base 12.When so assembled, there is sufiicient space between the envelope 29 andthe inside of the base 12 to accommodate the insertion of the lower endsof a pair of sleeve halves 30, as will be hereinafter more fullydescribed.

The sleeve halves 36, of substantially identical construction, serve asan expansible sleeve for reception at their lower end within thecompartment 13 of the base 12, and for clamping engagement with theexterior of the glass envelope 29.

Each sleeve half 30 is provided with one or a pair of ears 32 on oneside and an aperture 36 on the opposite side. Each such ear 32 isprovided with an aperture 34 for alignment with the aperture 36 on thecomplementary side of the associated sleeve half for insertion of arivet or hinge pin 38 therethrough. The apertures 34, 36 are locatedintermediate the opposite ends of the sleeve halves, but adjacent to thelowermost end thereof, the lower end of each half being slightly cutaway to provide for limited movement of the sleeve halves toward theupwardly diverging position shown in FIGS. 2 and 3. This position of thesleeve halves constricts the size of the lowermost end thereof forinsertion into the compartment 13 of the base 12 during the applicationof the shield to the base 12 and vacuum tube.

The interior of each shield half 30 is provided with non-removable rowsof highly efficient heat conductive spring elements 46 having surfaces48 defining a total generous heat dissipating area in pressureconfronting relationship with the exterior surface of glass envelope 29.The inside diameter of the interior compartment formed by such contactsurfaces 48 is slightly smaller than the exterior diameter of the glassenvelope 29 with which it is to be used, thus stressing such elementsupon application to the vacuum tube. By the nature of the application ofthe sleeve halves to the base 12, namely pressure applied to the upperends of the sleeve halves to close the shield, a high pressure isprovided between the surface 13 and bottom of the sleeve halves 30 bythe mechanical advantage provided for by the juxtaposition of thefulcrum point 38 with respect to the ends of the sleeve halves 30. Thebase 12 being bolted to the chassis 25, provides high contact pressurebetween the bottom of flange 15 and the chassis 25. The high pressurecontact at these interfaces provides a particularly effective heattransfer path for conducting heat from glass envelope 29 through theelements 46, sleeve halves 30, base 12, to the metallic chassis 25. Thespring elements also prevent scratching, scoring, or marking of theglass envelope, which might result from any sliding of the shield withrespect thereto.

The sleeve halves 30 are secured in clamping engagement with theenvelope 29 by means of a clamp element 42 in the form of a lid havingan annular side wall 43 of substantially the same diameter as theinterior of the base 12. This element 42 may be readily slipped over theupper ends of the sleeve halves 30, as shown in FIGS. 1 and 3, tomaintain the sleeve halves in a substantially parallel position. In thisposition the spring elements 48 are in pressure engagement with theexterior of envelope 29, thus insuring an effective heat path throughthe respective parts. This element 42 is also provided with a centralopening 44 for facilitating the circulation of air through the shield,which circulation is further facilitated by the diametrically spacedapart openings 26 in the base 12 and the spaces 47 between adjacent heatdissipating elements 46 as clearly shown in FIG. 4.

With reference now to FIG. 6 of the drawing, a slightly modified form ofmounting means 50 for the shield of the present invention, for use withstandardized Joint Army-Navy type tube sockets 52, is shown to include abase ring 56 having a pair of opposed spaced apart recesses 58 foraccommodating the heads 54 of the tube socket mounting screwstherewithin. Ring 56 is also provided with a pair of opposite, spacedapart indents 60 which open radially inwardly of the ring to accommodatethe passage of radially outwardly projecting detents 62 on the side wallof the tube socket 52.

The embodiment shown in FIG. 6 also includes a mounting ring 64 having aradially inwardly extending flange 65 with a pair of diametricallyspaced apart and radially inwardly opening indents 66 for receivingdetents 62 of tube socket 52. This inwardly extending flange 65 definesan upwardly facing, inclined surface 68 which is slidably engageablewith the lower portions of the detents 62 of the base 52 in response torotation of the ring 64 to clamp ring 64 in pressure engagement with themounting ring 56 upon the chassis of the equipment. Thus, the interior67 of the ring 64 serves in the same capacity as the interior 13 of thebase 12 of the aforementioned embodiment for slidably receiving thelower ends of the sleeve halves 30 therewithin, such sleeve halves beingreceived within the space between the tube socket 52 and the ring 64.

The base 12 of the embodiment illustrated in FIGS. 1 to 5, and the ring64 of the embodiment illustrated in FIG. 6, are both provided withradially inwardly projecting detents 41, 69, respectively, which may beof any desired length, and which are received within at least a por tionof a groove 39 formed upon the exterior of each sleeve half 30intermediate the hinge axis thereof and the lowermost ends thereof. Thisengagement eifectively locks the sleeve halves within the base uponapplication of the clamp element 42 thereto, thus withstanding all typesof impact and vibrational stresses during use.

' Another embodiment of the invention is illustrated in FIGS. 7 to 13.In this embodiment, two semi-cylindrical shield sleeves 80 and 82include widediameter base regions S4 and 86, respectively. Sleeves 80and 82 are plated on their interior surfaces at 81 and 83, respectively,with a material of good heat conducting properties (e.g. copper). A tubesocket mounting ring 88 secures a tube socket 16 and is held beneathchassis 25 by means of two mounting screws 89. The shield mounting ring85 includes an annular base 87 which may be secured to'the top ofchassis 25 by screws 89 passing through suitable apertures 90 in thebase, chassis, and socket mounting ring.

Shield mounting ring 85 includes a pair of upstanding semi-cylindricalwalls 91 and 92 integrally formed with base 87 and adapted to hold underpressure base regions 84 and 86, respectively, of sleeves 80 and 82. Asshown in FIG. 10, a pair of apertures 94 at the junction of wall 91 andbase 87 receive corresponding securing projections 98 of base region 84to ensurethe proper relationship between the tube and shield. Similarly,apertures 96 receive securing projections 100 of sleeve 82. To ensurepressure between the sleeves and the walls of the mounting means, theradii of base regions 84 and 86 are slightly greater than the radius ofwalls 91 and 92. In one oper ative construction, the outer diameter ofthe base region of the assembled shield was one inch, while the innerdiameter of the walls of the mounting means was approximately fourthousandths of an inch less.

Immediately above base region 84, the edges of sleeve 80 includesconcave and convex portions 101 and 102, respectively, which are adaptedto receive mating convex and concave portions 103 and 104, respectively,in the edges of sleeve 82 to form a socket-type hinge. The hingeportions of the two sleeves are properly shaped as shown to enable aslight pivotable movement from an upright position to the open positionshown in FIGURE 9. The shield sleeves are held together by twin eyelets109 and 110, which may be positioned in pivot holes 106 and 108 ofsleeves 81 and 82, respectively. 7 The eyelets are thereafter flangedover the inner surface of the sleeves as shown in FIG. 12 to pivotallysecure the sleeve sections together. When the shield is open, thediameter of the base region is effectively decreased, enabling theshield to be readily positioned within walls 91 and 92 of mounting means85. To permit rotation, each of the sleeve halves is cut away at itsbottom portion as shown at 115. In addition, when the shield isassembled, these cut-out portions will be adjacent the spaces betweenupstanding walls 91 and 92 to provide an air intake for coolingpurposes.

The resilient heat transfer and vibration damping means of thisembodiment comprise a plurality of separate, elongated spring elements120 as best shown in FIGURE 13. Sincethe individual spring elements areidentical only one will be explained. Each comprises a pair of closelyspaced, inner spring elements 121 and 122 whose curvedinner faces areadapted to contact vacuum tube 29. Inner elements 121 and 122 areresiliently connected with an integral outer, curved portion 123 byopposing diagonal portions 124 and 125. The exteriors of outer portions123 are soldered to copper plated sections 81 and 83 of respectivesleeves 80 and 82. This connection enables particularly excellent heat,transfer characteristics between spring elements 120 and sleeve halves80 and 82.

If desired, an entire liner of corrugated metal having the configurationillustrated in FIGURES Sand 13 may be secured to the individual sleevehalves and thereafter cut to form the individual spring elements. Forexample,

paste solder 126 may be extruded and deposited upon the exteriorsurfaces of outer portions 123 which are to contact the copper platedareas of sleeves and 82. After the liner has been properly positionedadjacent the plated sections, pressure may be applied to spread thepaste solder over the area of contact between the sleeve and the liner.Thereafter, the soldering may be accomplished by a conventionalinduction heating cycle. After the liner has been properly secured tothe sleeve halves, slots of about three hundredths of an inch maybe'made in the liner as indicated at 127 to form the individual Springelements described above. The assembly may thereafter be cleaned andchromated and at least the inner surface painted a dark color (e.g.black enamel).

To secure the shield sleeves together, a generally U- shaped closingwire 128 is employed in conjunction with a top eyelet 130 which isriveted into aperture 131 of tube sleeve 82. As shown in FIGURE 11,eyelet 130 includes an elongated, re-enforcing tab 132 and a smallprojection 134 immediately beneath the eyelet. The eyelet issecured inits proper position by bending projecting tab 132 over the top of sleeve82. Closing wire 128 includes an indented tongue 129 and is rotatablysupported in apertures 136 and 138 of sleeve 80, so that when the tubeshield is assembled, indented portion 129 may be received in eyelet 130to prevent the shield sleeves from parting. Closing wire 128 provides ahigh mechanical advantage to help close the sleeve halves underpressure. Tongue 129 is adapted to resiliently contact reenforcing tab132 to force the sleeves together to their closed position, at whichpoint tongue 129 is seated in the aperture of eyelet 130. The purpose ofprojection 134 is to prevent tongue 129 from being pushed down intocontact with sleeve 82.

The tube shield of this embodiment is applied to the tube in the samemanner as in the previous embodiment. After the mounting ring has beenproperly secured around the socket of the tube and the tube has beeninserted into the socket the shield halves are parted as shown in FIGURE9 so that they may be readily inserted into the mounting ring. Theshield is then positioned so that the securing projections 98 and ofbase regions 84 and 86 lie adjacent their respective apertures 94 and96. When the shield is properly situated, the sleeve halves are pivotedto their closed position, pushing the sleeve base regions 84 and 86outwardly against upstanding walls 91 and 92 where they may be securedunder pressure by means of closing wire 128. The increased pressuredecreases the contact resistance between the shield and the chassis andalso improves the vibration damping characteristics of the springelements 120. Similarly, the soldering of the individual spring elementsto the various sleeve elements improves the transfer of heat betweenthese components, thus producing a tube shield with considerablyimproved heat transfer characteristics.

Thus, a high efiiciency heat conductive, protective shield assembly hasbeen provided which will protect a vacuum tube against damage due toheat, vibration, and impact forces, substantially prolonging the usefullife of such equipment and minimizing replacement maintenance and repairthereof. A vacuum tube can be readily removed from the socket byremoving the clamp element and allowing the sleeve halves to pivot to anopen position while still mounted within the base ring. In the eventthat it is desired to remove the sleeve assembly from its base, this maybe readily accomplished with no loss of parts in view of the hingedlyconnected relationship of the sleeve halves which facilitates thehandling thereof as a single unit.

In actual use, the shield is located upon the tube with no downwardpressure along the glass of the tube. Once the shield has beenpositioned, it is closed upon the tube without placing any loadupon thepins of the tube either by axial or torsional loading thereof. Thisfeature thus allows for much higher pressure loading of the shield uponthe tube. Furthermore, since the pressure is released prior to removingthe shield from the tube, the removal can be effected without twistingthe contact pins or removing the tube from the socket.

In addition to serving as a mechanical shock shield and heat dissipator,this device also serves as an electronic shield for grounding stray RFsignals which might otherwise adversely affect the operation of thevacuum tube.

While the invention has been described with particular reference to theembodiments shown in the drawings, it is to be understood that this isnot to be construed as imparting limitations upon the invention, whichis best defined by the claims appended hereto.

What is claimed is:

1. A heat-dissipating vacuum tube shield comprising, in combination, abase, mounting means for securing said base in surrounding relationshipwith a tube socket, a pivotally expansible sleeve having one endreceivable within said base and the other end expansible to a greatercross-sectional area than the said one end to receive a vacuum tube andthe like, resilient elements in heat conduct-ive relationship with theinterior of said sleeve for pressure contact with the envelope of avacuum tube mounted upon said tube socket, and clamp means carried bysaid sleeve and adapted tosecure said heat conductive elements inpressure engagement with said envelope, the said expansible sleevecomprising a pair of semi-cylindrical sleeve halves tranverselypivotally connected together for restricted movement between a securedparallel position within said base and a released angularly openposition.

2. A heat-dissipating vacuum tube shield as set forth in claim 1,wherein said base comprises an annular ring receiving said one end ofsaid sleeve therewithin, whereby movement of said sleeve halves to saidparallel position elfects pressure engagement with said one end of saidsleeve halves with the interior of said ring.

3. A heat-dissipating vacuum tube shield according to claim 2, whereinsaid resilient heat conductive elements comprise a plurality of separateelongated members, each of said members including an outer surfacesoldered to the inner wall of one of said sleeve halves, a pair of innersurfaces adapted to engage the exterior surface of the vacuum tube, andresilient means interconnecting said inner and outer surfaces.

4. A heat-dissipating vacuum tube shield according to claim 3, whereinsaid clamp means includes a securing wire pivotally attached to one ofsaid sleeve halves and securing means for said wire attached to theother of said sleeves.

5. A heat-dissipating vacuum tube shield as set forth in claim 2,wherein said heat conductive elements comprise a plurality of yieldablefins integrally secured to the interior of said sleeve halves anddefining a substantially cylindrical compartment of slightly smallerdiameter than the diameter of a vacuum tube to be shielded in saidparallel position of said sleeve halves, said fins yielding in responseto engagement with the exterior of the glass envelope.

6. A heat-dissipating vacuum tube shield as set forth in claim 5,wherein the exterior of said sleeve halves intermediate said one endthereof and the pivotal connection therebetween defines an indent, andsaid ring includes a radially inwardly projecting detent receivablewithin said indent of said sleeve halves in the parallel position ofsaid sleeve halves to lock said sleeve halves in intimate assembly withsaid base.

7. A heat-dissipating vacuum tube shield as set forth in claim 6,wherein said base ring further comprises a radially inwardly extendingflange having an inclined surface facing toward said opposite end ofsaid sleeve, said flange having a radially inwardly opening indentaccommodating a radially outwardly projecting detent formed upon theside of the tube socket for wedging engagement upon said flange surfaceto secure said ring in intimate assembly with said tube socket.

8. A heat-dissipating vacuum tube shield as set forth in claim 7,wherein said clamp means comprises a cap member having an annular sidewall, said side wall releasa-bly receiving said opposite ends of saidsleeve halves therewithin for restricting radially outward separatingmovement thereof.

9. A heat-dissipating vacuum tube shield according to claim 1, whereinsaid heat conductive elements are soldered to the inner surfaces of saidsleeve halves.

10. A heat-dissipating vacuum tube shield according to claim 9, whereinat least a portion of said inner sur faces are plated with a materialhaving good heat conduction properties.

11. A shield for vacuum tubes and the like comprising, in combination, apair of sleeve halves, transverse pivot means to enable the sleevehalves to pivot transversely from a secured parallel closed position toa non-parallel open position, a base to receive one end of the sleevehalves and to be held in secure engagement therewith when the saidsleeve halves are in said parallel position, and means for holding thesleeve halves together in the secured parallel position in pressureengagement with the said base.

12. A shield for vacuum tubes and the like comprising, in combination, apair of semi-cylindrical sleeve halves, the sleeve halves beingtransversely pivotally connected intermediately of the ends thereof toenable the said sleeve halves to pivot transversely from a securedclosed parallel position to a non-parallel open position, a base toreceive one end of the sleeve halves and to be held in secure engagementtherewith when the said sleeve halves are in the said parallel position,and means for holding the sleeve halves together in the secured parallelposition in pressure engagement with the said base.

13. A shield as claimed in claim 12 and in which the region oftransverse pivoting is disposed near the base end of the sleeves.

14. A shield for vacuum tubes and the like comprising, in combination, apair of semi-cylindrical sleeve halves, the sleeve halves beingtransversely pivotally connected intermediately of the ends thereof toenable the sleeve halves to pivot transversely from a secured parallelclosed position to a non-parallel open position to receive the vacuumtube and the like therebetween, a base to receive one end of the sleevehalves and to be held in secure engagement therewith when the saidsleeve halves are in the secured parallel position, means for holdingthe sleeve halves together in the secured parallel position in pressureengagement with the said base, and resilient elements in heat conductiverelationship with the interior of the sleeve halves when the sleevehalves are in the said parallel position, at least one of the saidsleeves being provided with a cut-away extending below the point ofpivot to the said one end in order to enable movement of the lower endsof the said sleeves tothe open position.

15. A shield for vacuum tubes and the like comprising, in combination, apair of partial-cylindrical sleeves juxtaposed in parallel position withlongitudinal edges of one partial sleeve adjacent the longitudinal edgesof the other partial sleeve to form a cylindrical shell, thelongitudinal edges of the partial sleeves being transversely pivotedtogether to enable the said sleeves to pivot transversely from theparallel position to a non-parallel open position, a base to receive oneend of the partial sleeves when the said sleeves are in the non-parallelposition and to be securely engaged by the said one end of the partialsleeves as they pivot from the non-parallel position to the parallelposition, and means for holding the sleeves together in the securedparallel position in pressure engagement with the said base.

16. A shield as claimed in claim 15 and in which the sleeves aresemi-cylindrical having wide diameter base regions, and the base toreceive the sleeves comprises semi-cylindrical walls and an integralbottom, the wide diameter base regions having projections and thesemicylindrical walls having apertures to receive the said projections.

17. A shield as claimed in claim 15 and in which the pivot connection isnear the said one end and in which the longitudinaledges from the pivotconnection to the said one end comprises mating concave-convex portionsto form a socket-type hinge.

18. A shield as claimed in claim 17 and in which the pivot connectioncomprises pivot holes in the respective sleeves at the said longitudinaledges and twin eyelets adapted to be received by the pivot holespivotally to secure the sleeve sections together.

10 References Cited by the Examiner UNITED STATES PATENTS 2,050,838 8/36Hafecost et al. 174-35 X 5 2,080,913 5/37 Hafecost et al 174-35 X2,701,866 2/55 Chapman 174-35 X 2,807,659 9/57 Woods 17435 X 2,862,99112/58 Reardon 17435 X 2,893,704 7/59 Passman 174-35 X 10 FOREIGN PATENTS352,733 7/ 31 Great Britain.

DARRELL L. CLAY, Primary Examiner.

15 JOHN P. WILDMAN, JOHN F. BURNS, Examiners.

11. A SHIELD FOR VACUUM TUBES AND THE LIKE COMPRISING, IN COMBINATION, APAIR OF SLEEVE HALVES, TRANSVERSE PIVOT MEANS TO ENABLE THE SLEEVEHALVES TO PIVOT TRANSVERSELY FROM A SECURED PARALLEL CLOSED POSITION TOA NON-PARALLEL OPEN POSITION, A BASE TO RECEIVE OEN END OF THE SLEEVEHALVES AND TO BE HELD IN SECURE ENGAGEMENT THEREWITH WHEN THE SAIDSLEEVE HALVES ARE IN SAID PARALLEL POSITION, AND MEANS FOR HOLDING THESLEEVE TOGETHER IN THE SECURED PARALLEL POSITION IN PRESSURE ENGAGEMENTWITH THE SAID BASE.